J-PARC K1.8BRにおけるビームを用いたK N相互作...

T. Hashimoto@原子核媒質中のハドロン研究 III

J-PARC K1.8BRにおける K-ビームを用いたKbarN相互作用の研究

Tadashi Hashimoto (RIKEN)

for the J-PARC E15/E62 collaboration

1


Antikaon in nuclear medium

‣ KbarN interaction• Strongly attractive in I=0 (weekly attractive in I=1)• Good data above the threshold- kaonic hydrogen x-rays, low-energy scattering data

• Poor sub-threshold information

‣What will happen if K- is embedded in a nucleus?• kaonic nuclear states might exist.- dense matter? neutron star? mass reduction? partial restoration of CSB?

• Attractive Kbar-nucleus interaction is supported qualitatively.- kaonic atom x-rays

- (K,N) spectrum shape, K-/K+ ratio in pA collision, …

2

still not understood quantitatively…


Status of the “K-pp” study

‣ All theoretical studies predict existence of “K-pp”‣ Experimental observation cannot be explained

3Further experimental information with different reaction channels is important

pp→(“K-pp”K+)→ΛpK+

@Tp=2.85 GeVPRL104, 132502 (2010).EPJA 48, 183 (2012).

E27

back-to-back Λp pairstopped K- on 6Li, 7Li, 12C

PRL94, 212303 (2005).

``K"pp’’"like(structure(coincidence)(•  Broad(enhancement(~2.28(GeV/c2(has(been(observed(in(the(Σ0p(spectrum.(•  Mass: (BE: )

•  Width: •  dσ/dΩ``Kpp’’Σ0p =

•  [Theoretical value: ~1.2]

T.(Sekihara,(D.(Jido(and(Y.(Kanada"En’yo,(PRC(79,(062201(R)(((2009).

<10proton0coincidence0probability>π+dK+X,(XΣ0p(<2proton(coincidence(analysis>

d(π+,K+)X, Σ0p-tagJ-PARC E27

DISTO

FINUDA

[Kbar(NN)I=1,S=0]I=1/2, Jπ=0-

plot by Y. Ichikawa

PTEP2015,021D01


40% C.J. Batty et al. IPhysics Reports 287 (1997) 385445

Kaonic atoms lo4

F (a) c

1 ).&I n=3 IO3 B n=4 n=5 n

f

1

-I 10

0 lo 20 30 40 50 60 70 80 90 100 Z

Fig. IT. Shift and width values for kaonic atoms. The continuous lines join points calculated with the potential discussed in Section 4.2.

best-fit optical

Ref. [44]. For ease of reference, the complete data set listed in [44] will be referred to as ALL. The data set with 180 and 98Mo omitted will be denoted LESS, whilst the measurements for the two isotope pairs 160-180 and 92Mo-98Mo will be referred to as ISO.

- Shi

ft [e

V]W

idth

[eV]

Z (atomic number)

‣ Data points existacross the periodic table

• K-p: SIDDHARTA• K-d: no Data• Z = 2(He) ~ 92(U)- measurements in 1970’s & 80’s

not so good quality…

‣ Global analysis prefer a deep potential? - Re V ~ 150~200 MeV

• Phenomenologicaldensity dependent optical potential

• Chiral potential ( ~50 MeV )+ phen. multi nucleon terms.

Kbar-nucleus interaction from Kaonic atom data

4

E. Friedman and A. Gal, NPA 899( 2013) 60.

Phys. Rep., 287 (1997) 385.

C. J. Batty, E. Friedman, and A. Gal,Phys. Rep., 287 (1997) 385.

Ramos, Oset, NPA671(00)481

New systematic measurements with improved precision are important


J-PARC hadron hall

5

K1.8

K1.8BR

T1 target K1.1BR

KL

‣ Low momentum kaon beam• < 1.1 GeV/c• stopped K‣ Multi-purpose detector system

• Neutron TOF counter• Beam analyzer• CDS• Cryogenic target

(liquid H2 / D2 / 3/4He)

Features of K1.8BR


Experiments at K1.8BR‣All approved experiments investigate the KbarN interaction

• E15: Search for K-pp via 3He(K-, n)

• E31: Spectroscopic study of Λ(1405) via d(K-,n)

• E57: K-p, K-d X-rays

• E62(←E17) : Kaonic 3He/4He atom X-rays

6

-withdifferentchannels&processes-sensi3veindifferentenergyregion&isospin

1st physics data in 2013. x10 times data coming soon.

small data-set as an E15 calibration. requesting beam time.

1st-stage approval. start with K-p to confirm S/N.

Update with TES confirmed as 2nd-stage.

1.

2.


E15: “K-pp” search via 3He(K-,n)

7

Results of the 1st physics run1. Semi-inclusive 3He(K-,n)2. Exclusive 3He(K-,Λp)n


J-PARC E15 collaboration

8


In-flight K- reaction on 3He

9

+

nK-

qK~200MeV/c

quasi-elastic

pS pSK- 3He

+

1GeV/c

2

E15:$“K0pp”$search$via$3He(K0,n)$@pK=1GeV/c

+

p

p/-

n

RppK-

ppK- formation

CDS

CDS

NC

decay

decay

formation

for efficient “ppK” formation without 2NA backgroundY decay can be rejectedFormation & Decay

(quasi0free$KN)

14年5月15日木曜日

2NA should be suppressed Y decay can be separated

final goal:detect everything!

(@ 0°)

1.2~1.3 GeV/c


K1.8BR experimental area

10

J-PARC K1.8BR spectrometer

neutron countercharge veto counter

proton counter

beam dump

beam sweepingmagnet

liquid 3He-targetsystem

CDS

beam linespectrometer

K-

γ, n p

15m

500 mm0

solenoid magnet

vacuum vesseltarget cell

Beam Veto Counter

CDH

CDC

BPC

BPD IHDEF

K. Agari et. al., PTEP 2012, 02B011


Preliminary

J-PARC E15 1st stage experiment

11

))2

b/s

r/(M

eV

/cµ(

CD

S A×

/dM

Ω

/dσ

2 d

020406080

100120140160

M(K

+p

+p

)

Binding Energy [GeV]00.10.20.3

Data-decayΣBG

neutralBGcellBGaccidentalBG

2C

ounts

/ 1

0 M

eV

/c

0

5

10

15

20

25

30210×

)2,n)X missing mass (GeV/c-He(K32 2.1 2.2 2.3 2.4 2.5 2.6 2.7

Arb

itrary

unit

All

n-K→n-K

ns0K→p-K

)π)(π(πΛ→N-K

)π)(π(πΣ→N-K

K∆),π(π,NKπ*Y→N-K

]2 [GeV/cmissingp)nL, -He(K3p) in LI.M. (2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 30

2468

101214161820

Coun

t per

20 M

eV/c2

M(K+p+p)

M(K+p+p)

+

+reaction

K- 3He

K-pp n

p

p

Λ

π -

Formation 3He(K-,n)X

Decay 3He(K-,Λp)n

5 x 109 kaons(~ 1% of full proposal)


Formation channel Semi-inclusive 3He(K-, n)

12

Formation Channel, Semi-Inclusive 3He(K-,n)X

6

K-

CDH hit

CVC veto

BVC veto

, n

charge sweep out

NC hit


Semi-inclusive 3He(K-,n) at θn= 0

13

))2b/

sr/(

MeV

/cµ(

CD

S A×

/dM

Ω

/dσ2 d

020406080

100120140160

M(K

+p+p

)


Data-decayΣBG


2C

ount

s / 1

0 M

eV/c

0

5

10

15

20

25

30210×


Arb

itrar

y un

it

All

n-K→n-K

ns0K→p-K

)π)(π(πΛ→N-K

)π)(π(πΣ→N-K


))2b/

sr/(M

eV/c

µ(CD

S A×

/dM

Ω

/dσ2 d

020406080

100120140160

M(K

+p+p

)


Data-decayΣBG


2Co

unts

/ 10

MeV

/c

0

5

10

15

20

25

30210×


Arbi

trary

uni

t

All

n-K→n-K

ns0K→p-K

)π)(π(πΛ→N-K

)π)(π(πΣ→N-K


σ ~ 10 MeV/c2

FINUDA/DISTO/E27


!"#$!%&#'($)*+,-.Σ/0

!1234!"#$!536

789:;:,'<+5:=8

!>?2?!"#$!56 43

!"#$!%&#'($)*+,-.Σ/0

!@2?4!"#$!563

A?B,.C!DE8FG';H%69C!*/32IJ 32K3 32KJ 32J3 32JJ 32L3 32LJ

323

32J

>23

>2J

?23

?2J

I23

I2J

K23.!DE8FA3M%632?3;32>3;323332>3I>3C

!N*+,"5

!G!>3!O

8F

!N*+,"5

!G!>3!O

8F

!N*+,"5

!G!>3!O

8F

789:;:,'<+5:=8

AB,.C!DE8FG'9C!*/!-%6; ?>2I3 >2IJ >2K3 >2KJ >2J3 >2JJ >2L3

323

32J

>23

>2J

?23

?2J

I23

I2J

K23

H.!DE8FAM%6;32?3;32>3;323332>3I>3C

!"#$!%&#'($)*+,-.Σ/0

789:;:,'<+5:=8

?2?J ?2I3 ?2IJ ?2K3 ?2KJ ?2J3 ?2JJ

I>3C 32?3;32>3;323332>3

A?B,.C!DE8FG';P8%6I9C!*/

323

32J

>23

>2J

?23

?2J

I23

HH.!DE8FA;

M%6

Spectra&of&(KT,nK0)&events&on&p/d/3He

9

M(KT)

M(KT+p)

M(KT+p+p)

• p(KT,n)X

• d(KT,n)X

• 3He(KT,n)X

Fermi&motion

Fermi&motion

• K9p→K0$+$nfw

• K9d→(K9p)$+$nfwY*

subTthreshold&excess!

• K93He→(K9pp)$+$nfwY*N

subTthreshold&excess!

π

π

cf.&E31

Forward neutron specta on p/d/3He

14

spectrometer is well understood!!

expectedposition&width


d(K-,n)X with charged πΣ tag

15

d(K-, n)”X" %” Spectrum

We observed some events below the KN thresholdBoth - + mode and +- mode are included.

To be separated.

－＋－＋

11

-

“n”+

+

-“n”

-

+

- + mode

+- mode

n

n

NC

No separation btw. 2 charged modesNo acceptance correction

K- d)n "+ "- n events

“n”

NC

1.) K- d)K0 n nS 2.) K- d)n " %Forward

n

+

-

These two contributions areremoved.

K- beam

10

K- d)n "+ "- n events n

+ -

“ns”

NC

K0

K0

1.) K- d)K0 n nS K- beam

9

K0 & forward-going Σ contributionsare rejected

K. Inoue@HYP2015


)2,n)X missing mass (GeV/c-He(K32.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7

b /s

r/MeV

)µ (

CD

S A×

/dM

Ω

/dσ2 d

0

20

40

60

80

100

120

140Data

SimulationNΛNΣ(1385)NΣ(1405)NΛ(1520)NΛ

2NAnon-mesonic

What is the origin of the excess?

16

CHAPTER 4. SPECTRAL ANALYSIS 107

system when the neutron is requested to be detected with the NC. We can see almostall the fast neutrons are associated by a decay pion within the CDS acceptance.If the decay pion is out of the CDS acceptance, the other pion produced at the Σproduction should be detected with the CDH to be triggered. Then Σs which cannotbe reconstructed is further halved as shown in Fig. 4.3(right).

A realistic analysis of the simulated data successfully reconstruct Σs and removefast neutrons from their decays with a rejection efficiency of 85∼90% at below theK−pp mass threshold as shown in Fig. 4.4. Here the Σ± signal region was definedas |IM(nπ±)−mπ± | < 12 MeV/c2, which corresponds to about ±2σ of the invariantmass resolution.

Removal of neutrons from Σ decays

Now let us remove the fast neutron contribution from Σ decays in our experimentalspectrum. Figure. 4.5 shows the relation of the nπ± invariant mass and the neutronmissing mass. We can see a vertical line at the mass of Σ, while there is alsohorizontal line made by pions from K0

s decay after the charge-exchange reactions.Thus the contributions to be removed have the quasi-free peak to some extent asshown in Fig. 4.6(left).

Figure 4.6(right) is the neutron missing mass spectrum after the removal of fastneutrons from Σ decays, which is used in the rest of this section.

4.2.2 Non-mesonic two nucleon absorption

Kaons may be absorbed into multi nucleons. Actually, many events without pionemissions were observed in the stopped kaon experiment, such as,

K− + “NN ′′ → Y +N.

The total non-mesonic multi-nucleon absorption rate was obtained in the exper-iments with bubble chambers to be 0.16 ± 0.03 on 4He[62], but only ∼0.01 ondeuteron[63]. Larger targets yields the rate as large as 0.2 in the emulsion ex-periment. Although various interpretations to this behavior were reviewed in [64],the mechanism of non-mesonic multi-nucleon absorption process is still not well-understood. In the case of in-flight experiment, the reaction cross section of multinucleonic processes should be considerably small since the de Broglie wave lengthof kaon is much shorter compared to the distance of two nucleons. However, multi-nucleon process can produce fast neutrons. Then their possible contributions areworth to be examined.

First, we consider the non-mesonic two-nucleon absorption reactions (2NR), inwhich not only ground state of Λ,Σ but also hyperon resonances such as Σ(1385),Λ(1405)and Λ(1520) can be populated as,

K− +3 He → Y (∗) +N +Ns. (4.2)

ΛN/ΣN branches are negligibly smallΛ(1520)n branch < 2 mb/sr

nΛ* pspectator

NC

20 mb/sr @ θ=0Breit-Wigner with PDG mass&width

naively understood by attractive & absorptive potentialother possibilities are… 1. non-mesonic two-nucleon absorption: Λ(1405)n branch

• rather large cross-section ~ 5 mb/sr• U.L. of deeply bound states: 1 ~ 10% of Λ*n branch?


What is the origin of the excess?

2. Loosely-bound “K-pp” state• The excess corresponds to 1~2 mb/sr

• ~ 10% of quasi-elastic peak• Assumptions

• Fully attributed to the K-pp state • isotropic decay K-pp→Λp/Σp/πΣp

17

naively understood by attractive & absorptive potentialother possibilities are… 1. non-mesonic two-nucleon absorption: Λ(1405)n branch

• rather large cross-section ~ 5 mb/sr• U.L. of deeply bound states: 1 ~ 10% of Λ*n branch?

)2,n)X missing mass (GeV/c-He(K32.10 2.15 2.20 2.25 2.30 2.35

CD

SA

0.00.10.20.30.40.50.60.70.80.91.0

pRApp-Kp0YApp-KpY/App-K

Binding Energy [GeV]0.00.10.20.3

)2,n)X missing mass (GeV/c-He(K32.10 2.15 2.20 2.25 2.30 2.35

cut

YD

0.00.10.20.30.40.50.60.70.80.91.0

pRApp-Kp0YApp-KpY/App-K

Binding Energy [GeV]0.00.10.20.3

CDS tagging efficiency


Comparison with theoretical spectral functions

18

Experimental spectrum is similar to theoretical predictions with a loosely-bound state.(Λ(1405) production is not considered)

Theoretical Calculations

12

Koite

, Har

ada,

PR

C80(

2009

)055

208

integrated CS: ~mb/sr

integrated CS: ~0.1 mb/sr

• CS is roughly consistent with KH • Exclusive πΣN measurement is an important key for further study

E15 (BG subtracted)

E15 (BG subtracted)

semi-inclusive semi-inclusive

inclusive

inclusive

Yam

agat

a-Se

kiha

ra, e

t al.,

P

RC80

(200

9)04

5204

S.Ohnishi, et al., PRC88(2013)025204

T. Hashimoto@原子核媒質中のハドロン研究 III]2c [GeV/dMM2 2.1 2.2 2.3 2.4 2.5 2.6

)]2 cb/sr/(15

MeV/µ [ (Lab)o -14o 2dM/Ωd/2 σd 0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Fig. 4 Missing-mass spectrum of the d(π+,K+) reaction for two-protons coincidence and

the Σ0p decay branch events. The mass acceptance of the RCA’s are corrected. The spectrum

was fitted with a relativistic Breit-Wigner function (see the text for the detail). We found

the mass 2275 +17−18 (stat.) +21

−30 (syst.) MeV/c2 and the width 162 +87−45 (stat.) +66

−78 (syst.) MeV.

the miss-identification of π± in RCA. Red points with error bars in Fig. 2 (c) are the sum

of the pink points and blue line. The normalization constant C and the amplitude of the

flat component (blue line) were adjusted to minimize the differences between the black and

red points. Thus, the obtained one proton coincidence probability spectrum of the broad

enhanced region could be reproduced by the “K−pp” and flat background.

What is the nature of the “K−pp-like structure? It should have strangeness −1 and baryon

number B = 2 from the observed reaction mode, so that the hyper charge Y = 1. As for the

spin of the K−pp system, a K− is theoretically assumed to couple with a spin-singlet (S = 0)

p-p pair in S-wave (L = 0). So that the JP = 0−, presumably. Alternative view of the system

as a Λ∗p bound state [21] also predicts the bound state spin to be 0. There is also a theoretical

prediction of a (Y, I, JP ) = (1, 3/2, 2+) dibaryon as πΛN–πΣN bound state [22].

4. Summary. We have observed a “K−pp”-like structure in the d(π+,K+) reaction at

1.69 GeV/c with coincidence of high-momentum (>250 MeV/c) proton(s) in large emis-

sion angles (39 < θlab. < 122). A broad enhancement in the proton(s) coincidence spectra

are observed around the missing-mass of 2.27 GeV/c2, which corresponds to the bind-

ing energy of the K−pp system of 95 +18−17 (stat.) +30

−21 (syst.) MeV and the width of

162 +87−45 (stat.)

+66−78 (syst.) MeV. The branching fraction between the Λp and Σ0p decay modes

of the “K−pp”-like structure was measured to be ΓΛp/ΓΣ0p = 0.73 +0.13−0.11 (stat.) +0.43

−0.21 (syst.),

for the first time.

Acknowledgements

We would like to thank the Hadron beam channel group, accelerator group and cryogenics sectionin J-PARC for their great efforts on stable machine operation and beam quality improvements.The authors thank the support of NII for SINET4. This work was supported by the Grant-In-Aidfor Scientific Research on Priority Area No. 449 (No. 17070005), the Grant-In-Aid for ScientificResearch on Innovative Area No. 2104 (No. 22105506), from the Ministry of Education, Culture,Sports, Science and Technology (MEXT) Japan, and Basic Research (Young Researcher) No. 2010-0004752 from National Research Foundation in Korea. We thank supports from National ResearchFoundation, WCU program of the Ministry of Education, Science and Technology (Korea), Centerfor Korean J-PARC Users.

7/8

19


))2b/sr/

(MeV/c

µ (CDS A×

/dM 1/dm2 d

0

2

4

6

8

10

12

14

16

18

20

)/+N+RM(+p)RM(

)/+N+YM(+N)YM( (1405)+p

)RM(


Data-decayYBG

cellBGaccidental+neutralBG

2Cou

nts / 10 M

eV/c

0

50

100

150

200

250

300

350

Mðp!Þ # 2255 MeV=c2 of the K$pp candidate reportedby FINUDA [16].

The X production rate is found to be as much as the!ð1405Þð¼ !&Þ production rate, which is roughly 20% ofthe total ! production rate. Such a large formation istheoretically possible only when the p-p (or !&-p) rmsdistance in X is shorter than 1.7 fm [3,4], whereas theaverage N-N distance in ordinary nuclei is 2.2 fm. Thepp ! !& þ pþ Kþ ! Xþ Kþ reaction produces !&

and p of large momenta, which can match the internalmomenta of the off-shell !& and p particles in the boundstate of X ¼ !&-p, only if X exists as a dense object. Thus,the dominance of the formation of the observed X at high

momentum transfer (#1:6 GeV=c) gives direct evidencefor its compactness of the produced K$pp cluster.As shown in Fig. 4, the peak is located nearly at the "!

emission threshold, below which the N"! decay is notallowed. The expected partial width of K$pp, #N"!, mustbe much smaller than the predicted value of 60 MeV [2],when we take into account the pionic emission thresholdrealistically by a Kapur-Peierls procedure (see [20]). Thus,#non-! ¼ #p! þ #N" ¼ #obs $ #N"! ( 100 MeV, whichis much larger than recently calculated nonpionic widthsfor the normal nuclear density, #non-! # 20–30 MeV[7,21]. The observed enhancement of #non-! roughly by afactor of 3 seems to be understood with the compact natureof K$pp [4].The observed mass of X corresponds to a binding energy

BK ¼ 103) 3ðstatÞ ) 5ðsystÞ MeV for X ¼ K$pp. It islarger than the original prediction [2,8,9]. It could beaccounted for if the $KN interaction is effectively enhancedby 25%, thus suggesting additional effects to be investi-gated [4,22]. On the other hand, the theoretical claims forshallow $K binding [10–12] do not seem to be in agreementwith the observation. We emphasize that the deeply boundand compact K$pp indicated from the present study is animportant gateway toward cold and dense kaonic nuclearmatter [15,23].We are indebted to the stimulating discussion of

Professors Y. Akaishi and R. S. Hayano. This researchwas partly supported by the DFG cluster of excellence‘‘Origin and Structure of the Universe’’ of TechnischeUniversitat Munchen and by Grant-in-Aid for ScientificResearch of Monbu-Kagakusho of Japan. One of us (T. Y.)acknowledges the support of the Alexander von HumboldtFoundation, Germany.

[1] Y. Akaishi and T. Yamazaki, Phys. Rev. C 65, 044005(2002).

[2] T. Yamazaki and Y. Akaishi, Phys. Lett. B 535, 70 (2002).[3] T. Yamazaki and Y. Akaishi, Proc. Jpn. Acad. Ser. B 83,

144 (2007); arXiv:0706.3651v2.[4] T. Yamazaki and Y. Akaishi, Phys. Rev. C 76, 045201

(2007).[5] T. Yamazaki et al., Hyperfine Interact. 193, 181 (2009).[6] M. Maggiora et al., Nucl. Phys. A835, 43 (2010).[7] M. Faber, A. N. Ivanov, P. Kienle, J. Marton, and M.

Pitschmann, arXiv:0912.2084v1.[8] N. V. Shevchenko, A. Gal, and J. Mares, Phys. Rev. Lett.

98, 082301 (2007); N.V. Shevchenko, A. Gal, J. Mares,and J. Revai, Phys. Rev. C 76, 044004 (2007).

[9] Y. Ikeda and T. Sato, Phys. Rev. C 76, 035203 (2007).[10] D. Jido, J. A. Oller, E. Oset, A. Ramos, and U.-G.

Meissner, Nucl. Phys. A725, 181 (2003); V. K. Magas,E. Oset, and A. Ramos, Phys. Rev. Lett. 95, 052301(2005).

[11] T. Hyodo and W. Weise, Phys. Rev. C 77, 035204 (2008).[12] A. Dote, T. Hyodo, and W. Weise, Phys. Rev. C 79,

014003 (2009).

0

0.5

1.0

1.5

2.0

2.5

2150 2200 2250 2300 2350 2400 2450

2150 2200 2250 2300 2350 2400 2450

200 100 0

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

(a) large-angle proton: high-P (p)

(b) small-angle proton: low-P (p)

Γ = 118 (8)

M = 2267 (2)

M = 2267 (2)

Missing Mass ∆M(K) [MeV/c ]2

Missing Mass ∆M(K) [MeV/c ]2

M(Λ*+p

) = 2345

M(Λ*+p

) = 2345

M(K+p+

p) = 237

0M(K

+p+p) =

2370

M(Σ+π+

p) = 226

7M(Σ

+π+p) =

2267

Deviatio

nUNC/

SIM(arb

. scale)

Deviatio

nUNC/

SIM(arb

. scale)

B (K pp) [MeV]-

T

T

FIG. 4 (color online). (a) Observed DEV spectra of %MðKþÞof events with LAP emission [j cos"cmðpÞj< 0:6] and (b) withSAP emission [j cos"cmðpÞj> 0:6]. Both selected with large-angle Kþ emission [$ 0:2< cos"cmðKþÞ< 0:4].

PRL 104, 132502 (2010) P HY S I CA L R EV I EW LE T T E R Sweek ending2 APRIL 2010

132502-4

J-PARC E153He(K-,n)X @ 1 GeV/c

FINUDA(stopped K-, Λp)

DISTOpp→ΛpK+

J-PARC E27d(π+,K+)X, Σ0p tag


)°=0

lab

neb/

sr a

t µ

Upp

er li

mit

(

0

50

100

150

200

250

300Binding Energy [GeV]

00.050.10.150.20.250.30.35

= 100 MeVK

= 60 MeVK

= 20 MeVK

Intrinsic peak shape: Breit-WignerDecay mode: K-pp→Λp 100% (isotropic decay)

Assumptions

J-PARC E15 (U.L.) 30 ~ 300 μb/sr @ 0 deg. 0.5 - 5% of quasi-elastic

smaller than usual hypernucleus sticking

~ 0.1% of stopped K-

larger than Λ* @ 2.8 GeV

LEPS (γ+d) (U.L.) 1.5-26% of γN→K+π-Y

HADES ( pp @ 3.5 GeV ) (U.L.) 0.7-4.2 μb (Λ* ~ 10 μb)

95% C.L.

~8% of Λ*


Decay channel Exclusive 3He(K-, Λp)n

to be submitted soon…

20


Λpn identification

‣ Λpn final state can be identified exclusively: ~ 200 events

‣ Σ0pn contamination ~ 20%

21

n

Coun

tsper20M

eV/c

2

1GeV/cK-beam

p

πp

missingn

Λ

CDS

Λ!pπ-

σ~ 2 MeV/c2


Λpn exclusive spectrum

22


2468

101214161820

Coun

t per

20

MeV

/c2 M(K+p+p)

M(K+p+p)

Resolution: σ ~ 10 MeV/c2

at the K-pp threshold

Preliminary


Comparison with Phase space

‣ 2NA reaction K-+3He→Λ+p+ns seem to be very weak‣ 3NA reaction K-+3He→Λ+p+n seem to exist‣ Enhancement around the K-pp threshold

23

Exclusive&3He(KT,Λp)nmis&by&3NA

• The$spectrum$CANNOT$be$reproduced$only$by$3NA$• Clear$structure$is$seen$around$KNN$threshold$

– NOT+explained+by+any+2*step+reactions,+such+as+Λ*N!Λp 13

]2 [GeV/cmissp)nΛHe(Kp) of ΛM( 3 - events, 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 30

2468

101214161820

p nΛ3NA

0π p n Λ3NA

0 p nΣ3NA

p nsΛ2NA

Cou

nts

per 2

0 M

eV/c

2

2NA position

2NA

Preliminary Preliminary

TotalΛpnΣ0pn


Kinematics of the structure

‣ low-momentum transfer(=forward neutron) is enhanced ‣ isotropic decay?

24

Kinematics&of&the&Structure

• low9momentum$transfer$is$enhanced$• isotropic$decay

14

Mom.&Trans&vs.&IM(Λp) Λp&decayTangle&in&CM

x

x x xx xx

xx x

xxx

xxxxx

x xx x

x

xx

xxxx x xx

x xx

xxxxxx

xxx

x xx xx

x xxxxxx

xxxxxx

x

xxxx

x

x

xxxxx

xxxxx

xxx xxxxxxxxxxxxx

xxxx

xxxxxxxxxxxxxxxxxxxxx xx

xxx xx

x x

xxxxxxxx

xxxxxx

xxxxx

xxxxx

x

xx

x

xx

xxxxx x

xx

xx x xxxxx xx

xxx xx

xxx

xxxx

x x

2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9Mom

entu

m T

rans

fer [

GeV

/c]

0.2

0.4

0.6

0.8

1

1.2

]2 [GeV/cmissp)nΛHe(Kp) of ΛM( 3 - events, !"!#$%&'Λ!()!Λθ*+,-. -/01 -/02 -/03 -/04 / /04 /03 /02 /01 .

/

.

4

5

3

6

2

7

1

*+8

)9,

cosθΛ$=$1$rela.ve$to$the$Λp$frame

Preliminary Preliminary


Assuming Breit-Wigner

‣ ~ 15 μb, a few μb/sr at θn=0• not contradict with the forward neutron analysis- < 1~2 mb/sr excess in semi-inclusive neutron spectrum- theories suggest K-pp→Λp << K-pp→πΣp

25

Assuming&BreitTWigner

• χ29test$with$Breit9Wigner$and$3NA$backgrounds$– assume$isotropic$Λp$decay$as$a$function$of$mass$and$width

15

χ2/NDF=62.3&/49&

]2 [GeV/cmissp)nΛHe(Kp) of ΛM( 3 - events, 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 30

2468

101214161820

Cou

nts

per 2

0 M

eV/c

2 di-baryon

Mult i N abs.

-30 -25 -20 -15 -10 -5 0 5 10

60708090

100110120130140

2.35 2.36 2.37 2.38

mass difference from threshold [MeV]

Mas [GeV/c2]

χ2min +1 χ2min +2χ2min +3

KNN

thre

shol

d

Wid

th [M

eV] Preliminary

Preliminary


Λ(1405)ps→Λp conversion

‣ Difficult to distinguish from the “K-pp” experimentally.‣ Should be compared with quasi-free Λ*N

• < 5 mb/sr from forward neutron analysis• ~ 0.5 mb/sr from theoretical calc. on K-d.• a few percent conversion probability?

26

nΛ*

pspectator

p

Λ

Preliminary

further studies are ongoing…

Λ(1405): Breit-Wigner at 1405 MeV/c2, Γ=50 MeV (PDG)


Preliminary

Summary of E15 1st

‣ Around the threshold ‣ Some excess of the events

both in formation- and decay-channel

‣ Hint of S=-1 di-baryon state?

‣ explained by Λ(1405)?

‣Deeply-bound region ‣ bump-structure reported

by FINUDA/DISTO/E27, has NOT been observed with the current statistics.

‣ cross section strongly depend on the reaction?

27

))2

b/s

r/(M

eV

/cµ(

CD

S A×

/dM

Ω

/dσ

2 d

020406080

100120140160

M(K

+p

+p

)


Data-decayΣBG


2C

ounts

/ 1

0 M

eV

/c

0

5

10

15

20

25

30210×


Arb

itrary

unit

All

n-K→n-K

ns0K→p-K

)π)(π(πΛ→N-K

)π)(π(πΣ→N-K



2468

101214161820

Coun

t per

20 M

eV/c2

M(K+p+p)

M(K+p+p)

Formation 3He(K-,n)X

Decay 3He(K-,Λp)n

FINUDA/DISTO/E27

We will further investigate the sub-threshold

structure using x10 statistics data.

Data taking starts soon! ( Nov. 10 ~ )


E17→E62: Kaonic helium atom X rays

28

1. Introduction2. Detector: Transition-Edge-Sensor microcalorimeters

3. Feasibility test at PSI4. Simulation study for the J-PARC experiment


HEATES collaboration (J-PARC E62)

29

Updated proposal for J-PARC 50 GeV Proton Synchrotron

Precision Spectroscopy of Kaonic Helium 33d → 2p X rays

June 15, 2015

M. Bazzia, D.A. Bennettb, C. Beruccic, D. Bosnard, C. Curceanua, W.B. Dorieseb,J.W. Fowlerb, H. Fujiokae, C. Guaraldoa, F. Parnefjord Gustafssonf , T. Hashimotog,

R.S. Hayanoh∗, J.P. Hays-Wehleb, G.C. Hiltonb, T. Hiraiwai, M. Iioj, M. Iliescua,S. Ishimotoj, K. Itahashig, M. Iwasakig,l, Y. Mag, H. Noumii, G.C. O’Neilb, H. Ohnishig,

S. Okadag†, H. Outag‡, K. Piscicchiaa, C.D. Reintsemab, Y. Sadai, F. Sakumag,M. Satog, D.R. Schmidtb, A. Scordoa, M. Sekimotoj, H. Shia, D. Sirghia, F. Sirghia,

K. Suzukic, D.S. Swetzb, K. Tanidak, H. Tatsunob,i, M. Tokudal, J. Uhligf ,J.N. Ullomb,m, S. Yamadan, T. Yamazakih, and J. Zmeskalc

a Laboratori Nazionali di Frascati dell’ INFN, Frascati, RM, I-00044, Italyb National Institute of Standards and Technology (NIST), Boulder, CO, 80303, USA

c Stefan-Meyer-Institut fur subatomare Physik, Vienna, A-1090, Austriad Department of Physics, University of Zagreb, Zagreb, HR-10000, Croatia

e Department of Physics, Kyoto University, Kyoto, 606-8502, Japanf Department of Chemical Physics, Lund University, Lund, 221 00, Sweden

g RIKEN Nishina Center, RIKEN, Wako, 351-0198, Japanh Department of Physics, The University of Tokyo, Tokyo, 113-0033, Japan

i Research Center for Nuclear Physics (RCNP), Osaka University, Osaka, 567-0047, Japanj High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan

k Japan Atomic Energy Agency (JAEA), Tokai, 319-1184, Japanl Department of Physics, Tokyo Institute of Technology, Tokyo, 152-8551, Japan

m Department of Physics, University of Colorado at Boulder, Boulder, CO, 80309-0390, USAn Department of Physics, Tokyo Metropolitan University, Tokyo, 192-0397, Japan

∗Spokesperson†Co-spokesperson‡Co-spokesperson

- High-resolution Exotic Atom x-ray spectroscopy with TES microcalorimeter -


1. Introduction

30


Kaonic atom X-rays

31

3d

2p Strong interaction

Nuclear absorption

3d-2p X-ray ( ~6 keV )

Width : Γ2p

Shift : ΔE2p

(Coulomb only)

Unique probe of the Kbar-nucleus strong interaction at the threshold energy

kaonic helium case

Breakthrough in energy resolution with a novel cryogenic detector

FWHM resolution at 6 keV

150 eV (SDD)→ 5 eV (TES)


40% C.J. Batty et al. IPhysics Reports 287 (1997) 385445

Kaonic atoms lo4

F (a) c

1 ).&I n=3 IO3 B n=4 n=5 n

f

1

-I 10

0 lo 20 30 40 50 60 70 80 90 100 Z

Fig. IT. Shift and width values for kaonic atoms. The continuous lines join points calculated with the potential discussed in Section 4.2.

best-fit optical

Ref. [44]. For ease of reference, the complete data set listed in [44] will be referred to as ALL. The data set with 180 and 98Mo omitted will be denoted LESS, whilst the measurements for the two isotope pairs 160-180 and 92Mo-98Mo will be referred to as ISO.

- Shi

ft [e

V]W

idth

[eV]

Z (atomic number)

Kbar-nucleus interaction from Kaonic atom data

32

with improved energy resolution… 1. Precision measurements for

energy levels with small shiftand narrow width

2. Direct measurements of‘upper’ level widths• Determined by x-ray yield ratio so far• One-nucleon absorption could be separated

from multi nucleon processes

3. Charged kaon mass• Higher levels where

strong-interaction effect is negligible

4. Other hadronic atoms (Σ-,Ξ-)

C. J. Batty, E. Friedman, and A. Gal,Phys. Rep., 287 (1997) 385.

E.Friedman, A.Gal, NPA899(2013)60

He


K-He atom 2p level shift

33

deep shallow

Phenomenological Vopt(r=0) ~ - (180 + 73i) MeV

Chiral Vopt(r=0) ~ - (40 + 55i) MeV

K-4He -0.41 eV -0.09 eV

K-3He 0.23 eV -0.10 eV

Isotope shift (K-4He - K-3He) -0.64 eV 0.01 eV

a recent theoretical calculation J. Yamagata-Sekihara, S. Hirenzaki : — Strong-intaction Shift & Width calc.E. Hiyama : — Charge-density dist calc. for 4He&3He

(Gauss expansion method)

Choosing the following two typical models : [Pheno.] Mares, Friedman, Gal, NPA770(06)84 [Chiral] Ramos, Oset, NPA671(00)481

preliminary

Dominant systematic error (~0.15 eV)due to kaon-mass uncertainty will be cancelled. Width : 2 ~ 4 eV


2p L

evel S

hift

[eV

] 20

10

0

-10

-20

E1

E2 E3

@KEK-PS

(Japan)

@DAΦNE(Italy)

Publication year

: K - He3

: K - He4-

-

2006

2007

2008

2009

2010

2011

2012 . . .

SIDDHARTA

E570

3d → 2p transition ~ 6 keV x-rays

Present status

34

Theoretical calculations predict | ΔE2p | < 1 eV, Γ ~ 2 eV

1cm

J-PARC E17 with SDD J-PARC E62 with TES

1cm

± 2 eV

Precision goal

± 0.2 eV Width: sensitive to Γ > ~2 eV


2. Detector

35


Transition-Edge-Sensor microcalorimeters

Excellent energy resolution ~2 eV FWHM@ 6 keV Wide dynamic range Large effective area with multiplexing technique Portable & compact system

36

X-ray microcalorimeter17

a thermal detector measuring the energy of an incident x-ray photon as a temperature rise (= E/C ~ 1 mK )

Decay time constant= C / G ( ~ 500 μs )

e.g., Absorber : Bi (320 um × 300 um wide, 4 um thick) Thermometer : thin bilayer film of Mo (~65nm) and Cu (~175nm)

T

t

τ~CG

Absorber with larger “Z” (to stop the high energy x-rays)

AbsorberHeat capacity : C

Thermal conductance : G

Low temperature heat sink

~ pJ/K

~ nW/K

Thermometer

T

X-ray energy : E

TES = Transition Edge Sensor18

using the sharp transition between normal and superconducting state to sense the temperature

normal conducting sate

superconducting

sate

0 TemperatureRe

sist

ance

~ 100 mK

Width of transition edgeΔE~ a few mK

--> developed by Stanford / NIST at the beginning

Dynamic rangeEmax CTC/

Trade-off between dynamic range and energy resolution : ΔE ~ √Emax

( Johnson noise and phonon noise arethe most fundamental )

Energy resolution (σ)

E =

kBT 2C

Thermometer sensitivity

d lnR

d lnT 1023

applications : astrophysics (space satellite) etc.

a few mK

super-conducting

state

normalconductingstate

E = 2.355

rkBT 2C

↵

Emax

/ C

↵

↵ =

d logR

d log T


NIST TES system

37

J.N. Ullom et al., Synchrotron Radiation News, Vol. 27, 24 (2014)

Bi + TES

Au coated Si collimator

33 cm

1cmPhoto credit : J. Uhlig

‣ NIST designed cryostat‣ Pulse tube (60K, 3K) + ADR (1K, 50mK)‣ ADR hold time: > 1 day‣ Manufactured by High Precision Devices, Inc.

‣ Detector snout‣ 240 pixel Mo-Cu bilayer TES

30 ch TDM(time division multiplexing) readout‣ 1 pixel : 300 x 320 um2 → total ~ 23 mm2

‣ 4 um Bi absorber → efficiency ~0.85@6 keV

1 cm


3. Feasibility study at PSI

38


Feasibility test : πC x-ray measurement Aim : studying in-beam performance of TES Site : Paul Scherrer Institute (PSI) at PiM1 beamline Measured x-rays: πC 4f→3d transition ~ 6.4 keV

(strong-interaction effect is small)

39

BC1BC2

BC4carbondegrader

leadcollimator

π beam

TES arrays Carbontarget

x-ray tube

Top view

BC3

Lead shield

1~2MHz 170 MeV/c

10 cm


πC 4-3 X rays

40

π-atom peak with clear timing

correlation

FWHM ~ 7 eVPrelim

inary

Excellent energy resolution even in the hadron beam

Good timing resolution comparable with SDDs

Accurate energy calibrationusing Cr&Co lines

piC x-ray energiesagree with EM calc.

5 eV (beam off)→7 eV (beam on)[FWHM@ 6.4 keV]

< 0.1 eV accuracy @ FeKα

Experimental uncertainty±0.13(stat.)±0.09(syst.) eV


4. J-PARC experiment

41


K1.8BR experimental area

42

J-PARC K1.8BR spectrometer

neutron countercharge veto counter

proton counter

beam dump

beam sweepingmagnet

liquid 3He-targetsystem

CDS

beam linespectrometer

K-

γ, n p

15m

500 mm0

solenoid magnet

vacuum vesseltarget cell

Beam Veto Counter

CDH

CDC

BPC

BPD IHDEF

K. Agari et. al., PTEP 2012, 02B011


Experimental setup at J-PARC K1.8BR

43

K- beam

existing target system for Liq. Helium 3 & 4

(used for K-pp search, E15 expt.)

stop K- in a target

NIST TES system

Kaon beam detectors

Can we operate TES in the kaon beam at J-PARC?

Energy deterioration observedat higher beam intensities

Due to thermal crosstalksinduced by charged particle hits

(details in H. Tatsuno’s talk)

Simulation studywith realistic kaon beam condition


Simulation study for the J-PARC kaon beam

44

Energy (eV)0 2000 4000 6000 8000 10000

Cou

nts

/ 1 e

V

0

50

100

150

200

250

300DataMC(all)

beam)-πMC( beam)-µMC( beam)-MC(e absorption)-πMC(

Energy (eV)0 2000 4000 6000 8000 10000

Cou

nts

/ 1 e

V

0

50

100

150

200

250

300DataMC(all)MC(proton)

)-MC(e)+MC(e)γMC(

Figure 12: Measured TES self-triggered energy spectrum obtained at PSI experimentwith beam-on and no calibration x-ray (x-ray tube off) conditions, compared with thesimulated spectra. The left and right pannels include different disaggregated data withinitial beam particles (left) and particle species hitting on the TES (right), respectively.

Energy (eV)0 2000 4000 6000 8000 10000

Cou

nts

/ 1 e

V

0

10

20

30

40

50

60MC(all)

beam)-MC(K beam)-πMC( beam)-µMC( beam)-MC(e absorption)-MC(K

Energy (eV)0 2000 4000 6000 8000 10000

Cou

nts

/ 1 e

V

0

10

20

30

40

50

60MC(all)

)-πMC(MC(proton)

)-MC(e)+MC(e)-µMC(

)γMC(

Figure 13: Simulated TES self-triggered energy spectrum with J-PARC E17 condition for1-day data taking. The left and right pannels include different disaggregated data withinitial beam particles (left) and particle species hitting on the TES (right), respectively.

therefore only the events induced by beam. It should be noted that this beam intesity wastwice higher than that in the measurement described in Section 3.3 because of a wider slitsetting. The simulated spectrum was normalized by the number of incident beam, wherea flux ratio among the incident beam particles was deteremined by data measured withTOF method. The simulation indicates that the background mostly comes from electronshitting on TESs. Minumum ionization particles (MIPs) unfortunately give energy depositson the TES absorber (4-µm-thick Bi) in the region of interest (∼6 keV); thus direct hitsof MIPs on the absorber could be a dominant background. The trigger rate of TES wasestimated to be 0.64 /sec, whereas the experimental result is 0.71 ± 0.11 /sec. With thegood reproducebility of the hit rate and the spectral shape, we applied this simulationmethod to kaon-beam enviroment at J-PARC.

Figure 13 shows background spectra in the case of J-PARC E17 condition. Table 1summarizes the major input parameters of the beam condition and resultant TES triggerrates both for PSI and J-PARC cases. The last row in the table shows the energy depo-

18

e- beam incident

Good reproducibility of hit rate & spectral shape

Comparison of PSI data with the simulationSim result for each initial particles

TES trigger rate /pixel

Measured 0.71 ± 0.11 /sec

Simulation 0.64 / sec

J-PARC will be less severe compared with PSI

Table 1: Major input parameters for the simulations. The particle hit rates on the TESsystem obtained from the simulations are shown as well. Note that the rates at J-PARCis normalized by spill whose typical length is 2 seconds.

πM1 at PSI K1.8BR at J-PARCBeam momentum 173 MeV/c 900 MeV/cTotal beam intensity 2.8×106 /sec 8.0×105 / spillK−/π−/µ−/e− ratio —/ 40% / 5% / 55% 20% / 60% / 10% / 10%TES trigger rate / pixel 0.64/sec 0.17 /spillEnergy deposit on Si 152 MeV/sec 46 MeV/spill

sition rates on the silicon substrate evaluated in the same flamework. The comparisonbetween PSI and J-PARC cases indicates that the condition we operated TES at PSIwas more severe than the condition at J-PARC. Note that the trigger rates at J-PARCis normalized by spill whose typical length is 2 seconds. Assuming the phenomonologicalrelation concerning resolution deterioration with charged-particle hit rate as shown inFig. 9, we expect that in J-PARC E17, the TES spectrometer should work with a FWHMenergy resolution of better than 6 eV at 6 keV.

4.3 Estimation of the background in the final spectrum

Signal-to-background ratio is crucial for the precision spectroscopy of kaonic-atom x-raysdue to thier relatively low yields. Because the ratio is defined by the energy width of thedetector intrinsic resolution, the excellent resolution of TES naturally improves the ratio.On the other hand, as stated in the Section 4.2, the direct-hit events of MIPs on the TESabsorber will directly contribute to the continuum background unlike SDDs where thelarge energy deposits given by MIPs are out of the region of interest.

Two kinds of continuum-background comoponent are expected in the final spectrumafter K−-stop timing selection. One is asynchronous background which comes randamlywithout generating stopped K− trigger, the other is synchronous background correlatingwith the trigger timing.

Asyncronous background is propotionally reduced by the occupation ratio of thestopped-K− timing window. With the assumptions listed in Table 2, the occupationratio is estimated to be 3.6 × 10−3. Most of the backgrounds shown in Fig. 13 is theasynchronous background. The background yield without stopped-K− trigger at 6 keVis 30 counts / eV / day. Therefore, the asynchronous background in J-PARC setup isestimated to be 1.5 counts / eV during 2-week data taking with 50 kW beam power.

Synchronous background is expected to be significant in J-PARC. This originate fromthe inflight- and stopped-K− reaction on the materials around the target. Especially inthe K− absorption processes, even after the emission of the kaonic atom x-rays, secondarycharged particles are energetically produced via hyperon prodcutions and their decays.The synchronous background in J-PARC setup is estimated to be 6 counts / eV. Thismainly comes from the K− reactions at the target cell and various radiation shields.

As a result, the total background yield is estimated to be 7.5 counts / eV (= 1.5(asynchronous) + 6 (synchronous)) for 2-week data taking with 50 kW beam power.

19

(@ 50 kW)

( normalized by # of incident beam )


TES operation in the J-PARC kaon beam

45

TES should work well in the J-PARC kaon beam !!

J-PARC 0.17 / spill / pixel -> ~ 0.1 / sec /pixel

Energy resolution : 5 ~ 6 eV FWHM


Expected spectrum in J-PARC E62

46

Energy (eV)6000 6100 6200 6300 6400 6500 6600 6700

Cou

nts

/ 2 e

V

0

20

40

60

80

10050 kW beam intensity2 week data taking

2p→3d He3kaonic

1αFe K

2αFe K

2p→3d He4kaonic

Stat. precisions K-4He : ~0.2 K-3He : ~0.35

Assuming 6 eV FWHM resolution

240 counts

120 counts

Asynchronous bg. : 1.5 counts /eV Synchronous bg. : 6 counts /eV

Fe Kα intensities are controllable with applied voltage of x-ray tube

Stop-kaon tuning in Jun. 2016?

Physics data taking in 2017?


Summary‣We investigate the KbarN interaction using K- beam at J-PARC K1.8BR

‣We have started data taking !• E15 1st physics run has been successfully performed- some structure found around the threshold

- no significant structure in deeply bound region• H2/D2 target data as calibration- d(K-,n)πΣ

‣More data will come soon.• E15: 2nd physics run with x10 statistics from the middle of Nov. • E31: Λ(1405) via d(K-,n)• E57: K-p x-rays followed by K-d x-rays.• E62: KHe x-rays with TES.

47

J-PARC K1.8BRにおけるビームを用いたK N相互作...

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Transcript of J-PARC K1.8BRにおけるビームを用いたK N相互作...

J-PARC K1.8BRにおける ビームを用いたK N相互作...

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Transcript of J-PARC K1.8BRにおける ビームを用いたK N相互作...

J-PARC K1.8BRにおけるビームを用いたK N相互作...

Transcript of J-PARC K1.8BRにおけるビームを用いたK N相互作...